[vsnet-grb-info 4855] GRB 070628: Swift XRT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6587
SUBJECT: GRB 070628: Swift XRT refined analysis
DATE:    07/06/29 00:01:58 GMT
FROM:    Matteo Perri at ISAC/ASDC  <perri at asdc.asi.it>

M. Perri, G. Stratta (ASDC)  and S.T. Holland (CRESST/GSFC/USRA)
report on behalf of the Swift XRT team:

We have analysed the first 3 orbits of Swift XRT data from the possible
burst GRB 070628 (Holland et al., GCN Circ. 6584). Using an exposure
time of 6.3 ks the refined XRT position is RA (J2000) = 115.275833,
Dec (J2000) = -20.279750, corresponding to:
RA(J2000) = 07h 41m 06.2s
Dec(J2000) = -20d 16' 47.1"
with an uncertainty of 3.5" (90% containment). This is 0.5 arcmin from
the BAT position (GCN Circ. 6584) and 1.4 arcsec from the UVOT position
(Gronwall et al. GCN Circ. 6585).

The XRT light-curve in the time interval from T+116s to T+14ks shows
a fading behavior with superimposed flaring activity. More data are being
collected to monitor the light-curve evolution.

The X-ray spectrum covering the time period from  T+1.1ks to T+14ks
is well fit by an absorbed power law with a photon index of  2.2 +/- 0.1
and a total column density of NH=(7.5+/-0.7)e21 cm**-2. We note that
the Galactic column density in the direction of the source is
7.35e21 cm**-2 (Dickey & Lockman 1990).

This circular is an official product of the Swift XRT team.